Solar array max for flexmax80

Discussion about the FM100, FM80, and FM60 Charge Controllers

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dieselherb
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My RE system: 12 300W panels, Outback Flexmax80, Ames 48V 3000W inverter, 8 6V 210AH golf cart batteries

Solar array max for flexmax80

Post by dieselherb »

I have 12 300W panels 27+V 6.9amp. What is the max I can run thru the flex80? 48V system 8 6V deep cycle batteries, 3000W 48V inverter. How would I wire this?
Thanks
raysun
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Re: Solar array max for flexmax80

Post by raysun »

The FM80 is rated at 80A charging current, so the maximum PV array for a 48V battery is 80A x 48V = 3840W.

The 12 300W PV panels fit comfortably within this limit.

The other rated maximum for the FM80 is 150V array voltage. If the panels are rated at V(oc) ~ 27V then 4 panels could be wired in series, and 3 parallel strings wired into a combiner box (4Sx3P array).

The final specification limit is maximum charging current the battery will accept. For flooded lead acid battery blocks, its usually 10% of the C20 AH capacity. (e.g.: If the C20 capacity is 200AH, the maximum charge rate is 20A.) The FM80 has a current limit setting that can "throttle" the charge current to the battery requirement.

FWIW, I live in an area where lots of off-grid folks use the GC2 style golf cart batteries. While they are deep cycle batteries, they are not ideally suited for solar power system use, consequently, their service life is relatively short, even with proper maintenance. My advice is to take advantage of the (typically 1 year) replacement warranty. In the month before the warranty expires, take the battery blocks in and exchange them for new ones. Use the new ones as long as they last. Over the next 2 or so years, save your pennies for purpose-designed solar power deep cycle batteries. In that time you can do plenty of research on the subject (this forum is a great place to start) and prepare for a battery that can last a decade or more.
pss
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Re: Solar array max for flexmax80

Post by pss »

Please clarify that your 300 watt panels are only VMAX 27 volts. Most panels of that power are 37-39 volts so 3 series and 4 parallel strings is safe.
raysun
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REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
Honda EU7000is gas fuel generator

Re: Solar array max for flexmax80

Post by raysun »

pss wrote: Mon Jun 07, 2021 8:54 pm Please clarify that your 300 watt panels are only VMAX 27 volts. Most panels of that power are 37-39 volts so 3 series and 4 parallel strings is safe.
Good point.
dieselherb
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Re: Solar array max for flexmax80

Post by dieselherb »

I looked at all the panels, the info tags have faded away can't read anything in them. I measured output on 1 yesterday it was 43V amps were 20 and climbing. Multimeter stopped at 20, wires were melting.
pss
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Re: Solar array max for flexmax80

Post by pss »

You need some professional guidance. You wrote 43v 20 amps. That would be 860 watts of power. So it is unclear where you obtained this measurement from and how. The whole array, one string of panels in the array or something else.
dieselherb
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My RE system: 12 300W panels, Outback Flexmax80, Ames 48V 3000W inverter, 8 6V 210AH golf cart batteries

Re: Solar array max for flexmax80

Post by dieselherb »

Info was from 1 panel. Don't know if I can trust the mulimeter? But it worked fine on other items I tested, batteries.
pss
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Re: Solar array max for flexmax80

Post by pss »

Multimeters have scales on them for volts and only clamp on meters measure amps and they require a skilled user familiar with the tool. One panel cannot be 800 watts or melt wires. You need help to avoid electrocuting yourself.
706jim
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Re: Solar array max for flexmax80

Post by 706jim »

My multimeters have a 10 amp DC setting. I know they don't like it (will overheat if left on continuously) but should be capable of testing the output of pretty much any single panel.
sbrownian
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Re: Solar array max for flexmax80

Post by sbrownian »

Fluke 87 I have is rated at 10 amps, but will handle up to 20 amps for no more than 30 seconds. (From the J. Fluke spec page.)

It does have a 'slo-blow' fuse in the current loop, however. So far, I haven't had to replace it. (Yet..🙄)
Information, you get not; if incorrect question, you ask..
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